I have heard quite a few rumours that the new Met Police 145's will be used for more of a paramilitary / police role, 2 crew, winch equipped - Presumably in light of the terrorist threat and imminent olympics. I have flown for both the military and police, and can't help but think that the 2 should be kept apart. Street policing to be done by civilian pilots, and winching / absailing (anti-terrorist work) to be conducted by dedicated military crews who are well practiced in this role.
Of course, as I stated above, this could all be the rumour mill at work, but I believe that police forces in other European cities take on these additional responsibilites, so it isn't entirely over active imaginations !